Most malicious program like biruses trojans keyloggers and others are based upon the principle that they can be automatically loaded into the memory each time windows boots. This automatic start can eaisly be configured through registry. hence on most occassion it is good idea for administrator to disable the automatic startup of program.this can be done through following registry tweak.

1: GO TO run then type in regedit.exe and open it.

2:HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\explorer



3:Within the above registry key it is possible to create a number of new DWORD entries each with a slightly          different functions.(To create a DWORD value right click on the right pan of registry windows and save it.then    modify it and change its value to 0(for enabling automatic startup)  or 1(for prevent automatically start up).

 
DWORD Entry Function(what it does)
DisableLocalMachineRun Disable all application from automatic
start up during all sessions on that
machine.
DisableLocalMachineRunOnce Disable all application from automatic
start up during next sessions on that
machine.
DisableCurrentUserRun Disable all application from automatic
start up during all sessions for paricular
users.
DisableCurrentUserRunOnce Disable all application from automatic
start up during next sessions for paricular
users.

4:change value to 1 or 0.
5:exit from registry and restart the session of machine by logging off it.